1. Field of the Invention
The invention generally relates to luminaires and particularly to luminaires intended for ceiling mounting in either recessed or surface-mounted applications for “washing” an adjacent wall with light as well as other applications.
2. Description of the Prior Art
Luminaires intended for directing light onto vertical surfaces such as walls often fail to provide a visually smooth distribution of light on the vertical surface intended to be illuminated. Such luminaires, generally referred to as “wall wash” luminaires, are typically mounted in a ceiling in proximity to the vertical surface that is to be illuminated. In providing the goal of a smooth distribution of light on a vertical surface of an adjacent wall, it is intended that visible striations or noticeably defined changes in brightness on the vertical surface be minimized or eliminated. Since the accomplishment of a smooth illumination gradient on such a vertical surface is a goal rather than a realistic expectation, it is at least intended in the art to provide an illuminance on said surface having gradations that are sufficiently gradual so as to reduce the affects of variations in brightness such as can take the form of bright or dark lines, bands, scallops and the like such as can be visually distracting. Wall wash luminaires universally employ reflective surfaces configured not only to direct light from lamping onto an adjacent vertical surface but also to smooth the light pattern on said surface. A judicious choice of reflective material as is usual in the prior art, typically diffuse or semi-specular in nature, has previously been considered desirable for smoothing of a light pattern on a vertical surface albeit at the cost of efficiency loss when considering the lumens delivered to the vertical surface by lamping of a particular power level. Diffuser lenses have also been used for similar purposes and with similar results including losses. Luminaires configured with “small apertures”, that is, small in the dimension perpendicular to the “longitudinal” dimension of the luminaire, particularly suffer from efficiency losses when reflectors employed in such luminaires are formed of diffuse or semi-specular reflective material. Luminaires with square apertures as well as other shapes can also exhibit such losses. Further, the differences in brightness between the lamping as compared to lamp “images” in the reflected material produce further difficulties in providing the quality of illumination on a vertical surface that is desired in the art when light from the lamp and from the reflector are both incident on the wall. The use of highly reflective and highly specular reflective material in such luminaires increases the efficiency of light directed onto the vertical surface, and thereby illumination levels realized on the vertical surface, and also greatly reduces differences between the brightness of light illuminating the wall directly from lamping as opposed to the brightness of light reflected from reflectors used in such luminaires. However, utilization of highly specular reflective material in such luminaires provides no panacea in intended results due to the fact that the behavior of highly specular materials in optical environments are extremely sensitive to design errors as well as manufacturing and assembly tolerances. Accordingly, the use of highly specular reflective materials as reflectors in small aperture luminaires as well as other luminaires does not necessarily produce the desired visual appearance of illumination washing a vertical surface or wall.
Wall wash luminaires mountable in ceilings of varying description have previously been provided in a multitude of configurations including downlighting luminaires having circular apertures such as are disclosed by Ling in U.S. Pat. No. 5,535,110 and Leadford in U.S. Pat. No. 5,800,050. Ng et al, in U.S. Pat. No. 6,350,047, and many others, also provide wall wash luminaires intended to be mounted in recessed applications in ceilings whereby at least a portion of that light generated within the luminaire is directed onto at least portions of a wall adjacent to the location wherein the luminaire is mounted within a ceiling. In luminaires of the kind just noted, lamping typically mounted in a vertical orientation is utilized and is generally not tubular fluorescent lighting of a length generally greater than approximately six to ten inches. Wall Wash luminaires employing elongated tubular fluorescent lamping such as T12, T8 and even T5 lamping presently exist as can be appreciated by reference to U.S. Pat. No. 4,564,888 to Lewin et al which discloses a substantially elongated luminaire configured with an elongated reflector for directing light onto a wall from a substantially elongated and generally rectangular aperture. Crane, in U.S. Pat. No. 5,146,393 also discloses a luminaire intended to wash an adjacent wall with light from a location recessed within a ceiling adjacent to the wall. While the apertures of the Lewin et al and Crane luminaires are not necessarily of the “small aperture” kind, the apertures of the luminaires disclosed in these two patents are rectangular and utilize elongated fluorescent lamping. While lamping-such as T5 lamping can be used in prior wall wash luminaires and even in the rectangular aperture luminaires disclosed in certain of the above-noted patents, it is to be understood that presently available wall wash luminaires have not exhibited performances approaching the goal of a visually smooth distribution of light on a vertical surface in linear wall wash configurations in luminaires using highly specular materials unless provided with a lens. It is therefore a particular intent of the present luminaire configurations to produce an acceptably smooth distribution of light on a vertical surface from a wall wash luminaire, particularly a small aperture luminaire, as can be mounted in recessed or surface-mounted applications in a ceiling at a distance from the vertical surface to be illuminated such that the cross-sectional aperture of the luminaire is small relative to the distance of the luminaire from a vertical surface that is to be illuminated. Luminaires configured according to the invention are configured to utilize highly reflective and highly specular reflective materials as reflector elements and are further configured to provide visually smooth lighting distributions on adjacent vertical surfaces such that striations and/or alternating relatively light and dark areas are reduced or visually eliminated, thereby providing a substantial advance in the art.